1. Field of the Invention
The present invention relates to a radio-frequency radiocommunication apparatus for transmitting/receiving radiocommunications in a range from a microwave band to a milli-wave band.
2. Description of the Related Art
A radiocommunication apparatus for transmitting/receiving radiocommunications in a range from a microwave band to a milli-wave band is structured, for example, as shown in FIG. 7. In FIG. 7, a transmitter 100 includes a baseband input terminal 101, a baseband amplifier 102, an FM modulator 103 using a voltage controlled oscillator, a frequency up-converter 104, and an antenna 105.
On the other hand, a receiver 110 includes a baseband output terminal 111, an FM demodulator section 112, a frequency down-converter 113, a local oscillation section 114, and an antenna 115.
In the transmitter 100, for example, a channel signal representing a image and a sound is input to the baseband input terminal 101, and this signal is amplified by the baseband amplifier 102. The amplified signal is FM-modulated by the FM modulator 103, and the FM-modulated signal is up-converted to a milli-wave band signal by the frequency up-converter 104. This milli-wave band signal is radiated from the antenna 105 into the air.
On the other hand, in the receiver 110, a milli-wave band signal is received by the antenna 115, and down-converted by the frequency down-converter 113 into a low-frequency signal. The low-frequency signal is demodulated by the FM demodulator section 112, and the demodulated signal is output from the baseband output terminal 111. The signal output from the terminal 111 is sent to a display apparatus or a monitor apparatus to reproduce the image and the sound.
The transmitter 100 and the receiver 110 each include a local oscillator (not shown in the transmitter 100) for up-converting an FM output from the FM modulator 103 to a milli-wave band signal or for down-converting a milli-wave band signal to a low-frequency signal. The conventional local oscillator has a fixed oscillation frequency, and has no function for switching an oscillation frequency. Thus, the frequency of a milli-wave band signal transmitted between the transmitter 100 and the receiver 110 is fixed to a predetermined value.
Furthermore, although the conventional antennas 105 and 115 are flat antennas, both of them have no function for adjusting the direction thereof. Therefore, for example as shown in FIG. 8, the transmitter 100 and/or the receiver 110 are mounted on a three-leg stand 109, and the direction of each of the transmitter 100 and the receiver 110 is adjusted by adjusting the three-leg stand 109.
However, in the conventional radiocommunication apparatus as described above, the receiver often receives unintended milli-wave band signals having the same frequency as that of an intended signal, whereby radio interference is caused in the receiver. When such radio interference is caused, effects of the radio interference can be reduced by changing a transmission route for a radio signal between the transmitter and the receiver. However, the transmitter and/or the receiver are contained in a metal case, and the metal case containing the transmitter and/or the receiver is supported on a three-leg stand so as to fixed thereto. Such a radiocommunication apparatus has the height of at least 100 cm or more, and the width and the length of 20 cm or more. Thus, in order to carry and =manipulate such a large apparatus, a large manpower is required.
Furthermore, the conventional radiocommunication apparatus cannot transmit/receive radio waves at a level higher than the top of the three-leg stand. Thus, even when the transmission route for radio signals is changed, the radio signals are often blocked by various obstacles.
Furthermore, in the conventional radiocommunication apparatus, a display apparatus is provided separate from the transmitter and/or the receiver. Accordingly, it is difficult for a user to carry the radiocommunication apparatus and the display apparatus with her/him. In addition, the movable range of the transmitter and/or the receiver is restricted. Thus, there is a limitation in preventing radio interference by the movement of the transmitter and/or the receiver.